Motors are generally cooled by air, water or other cooling medium. Water cooling can provide a motor with an excellent cooling effect, thus enabling the motor to achieve a higher output power with a given cost or achieve a given output power with less used materials and a lower cost. Compared to air-cooled motors, water-cooled motors typically have less noise. Therefore, water-cooled motors are of relatively high economic and practical value for a variety of industries.
Existing water-cooled motors used in motor-pump units can be categorized into several types in terms of their structure. Motors of one of these types include a hollow helical aluminum tube embedded in the motor housing during the manufacture thereof by die casting. Although such motors can be effectively cooled by circulating water in the hollow helical aluminum tube, they have high structural complexity and manufacturing cost. Chinese Patent Publication Nos. CN201450384 U and CN201937382 U disclose motors of another type which employs a structure of a double-walled aluminum cylinder. In this structure, water-tight ribs are evenly distributed between two cylindrical walls; a cover is provided on each of the two ends of the cylinder; and the cover is engraved with water flow grooves. As this structure is composed of a large number of separable parts, it also suffers from high complexity and high manufacturing cost. In addition, due to a low sealability, the structure is vulnerable to water invasion and thus has a high safety risk. Chinese Patent Publication No. CN101663483A discloses a structure of a further type which provides a plurality of injection-molded ribs on inner surface of a plastic housing to form zigzag water flow paths between the plastic housing and the motor cooling housing. This structure is simple and has a lower cost. However, the mode for forming the plastic housing requires the employment of a complex mold with a number of core-pull features, which leads to a high possibility of manufacturing failure in the injection molding process. Additionally, the zigzag paths cause water flows to experience multiple 180 degrees turns in their advancing direction, which lead to a low water flow rate for a given cross-sectional area.
Chinese Patent Publication No. CN102510158A discloses a water-cooled motor with helical water flow grooves. Referring to FIG. 1, an inner housing 2 of the water-cooled motor has an external circumferential surface on which there are formed a plurality of helical water flow grooves 2.0. A circular water-collecting groove is formed at each end of the housing extending along the external circumferential surface, wherein a first circular water-collecting groove 2.1 is formed at a first end and a second circular water-collecting groove 2.2 is formed at a second end. Each of the helical water flow grooves 2.0 extends several equally spaced turns along an axis of the motor and connects the two water-collecting grooves at its two ends. Each of the two water-collecting grooves is provided with two water-splitting plates 2.3. The two plates 2.3 of the first water-collecting groove 2.1 divide the groove 2.1 into a first water inlet groove 2.11 and a first water outlet groove 2.12. The two plates 2.3 of the second water-collecting groove 2.2 divide the groove 2.2 into a second water inlet groove 2.21 and a second water outlet groove 2.22. The first water inlet groove 2.11 and the second water outlet groove 2.22 are interconnected and are further connected to a first water inlet connector 2.11′ and a second water outlet connector 2.22′, respectively, both disposed on an outer housing 1 of the motor. The second water inlet groove 2.21 and the first water outlet groove 2.12 are interconnected and are further connected to a second water inlet connector 2.21′ and a first water outlet connector 2.12′, respectively, both disposed on the outer housing 1. As such, two water inflows and two water outflows can be formed by connecting to an external water supply, thus forming a cooling loop with the water inflows and water outflows in lateral symmetry with respect to the motor axis.
In order to achieve the opposite water flows, two connectors are provided on one side and another two connectors are provided on the opposite side of the outer housing (i.e. four connectors in all), which leads to a high structural complexity, high manufacturing and assembly difficulties of the outer housing, and high risk of motor failure causing water leakage. Further, in order to meet the need of heat transfer, the motor housings are formed by metallic materials, and as the thread grooves are formed in the inner housing and the inner housing is integrally formed with the water-splitting plates, the housings can only be manufactured by pressure casting which is a process prone to produce motor housings with gas pores therein, namely the cast structures are not dense. These gas pores may direct water, during the use of the motor, from the grooves into the middle of the motor and hence probably cause electric leakage and electric shock accidents.
Therefore, there is an urgent need in this art for a water-cooled motor capable of a uniform cooling effect and high cooling efficiency while having a simple structure, high manufacturability, low cost, high water tightness, high safety and reliability.